Making A Scoop Part 1

Note:  I actually wrote this blog yesterday in Word because I couldn't publish it due to not having an internet connection -- we were without power for two days as explained below.

For the last few weeks I have been working feverishly on a scoop that I wanted to have ready before the regional race at Summit Point on July 15th.  The scoop design has been bouncing around in my head for months so it felt good to be able to focus on making it.  However, the storms that blew through the Washington DC area Friday night have greatly hampered my planned weekend progress.  A tree fell on the garage roof and we have been without power since about 10:30 pm Friday night.  Luckily I had the generator that we use for racing in the shed so we have some power and I bought a portable Air Conditioner Saturday morning so the house isn't too hot.  On reason I bought that is so that I can use it in the garage after power is restored.  :)  I can't do much work on the scoop without power but I can get to the internet with a mobile broadband stick so I figured I would update the blog -- it has been a while anyway!

Before I get into the making of the scoop, the reason why it is important is because air intakes work much better if there is a low pressure area (created by having air go through a small hole into a larger chamber) and you also want the air to be as cool as possible.  The engine came with a K&N cone air filter and I can certainly run the car with just that filter.  But I think the engine should create a little more hp with a good scoop/cold air box and I’m going to use a rectangular panel air filter.  When the scoop is finished, it will be comprised of two pieces – a bottom piece that holds the air filter and attaches to the throttle body and a top piece that will be in the air stream.  The two will be joined in a manner that I haven’t decided on yet but most likely 10-32 screws.  There are a few ways to create pieces like this.  One way is to shape styrofoam (the type used for packing things) cover it with clear packing tape (this is necessary because fiberglass resin melts the styrofoam), fiberglass over it, and then use laquer thinner to desolve the styrofoam after the fiberglass has hardened.  It is a good, quick way to make something but the piece ends up being pretty rough and a lot of work needs done with bondo to make it look good. 

I'm mainly using the two part foam that I have used in other areas of this project.  This foam does not dissolve when coming in contact with fiberglass resin or lacquer thinner.  The scoop is going to sit in the engine bay behind my head and will be underneath the tail section in the engine bay.  First, I took some measurements and got a rough idea of how big of a piece of foam I needed to work with.  I created my own box, filled it with foam, and let it harden.

I then sanded it down to look more like a cube and marked grid lines on it to help me shape it symmetrically. 

I soon realized that I was going to need some more foam for the scoop opening.  I had some pink foam laying around so I decided to use that.  However, I wished I had used more of the two part foam because the pink foam has a much lower density and working with it was a little bit more of a challenge.  I joined the two pieces with some ¼” wooden dowel pins and some bondo.  I made sure that I only spread the bondo in the center where I wouldn’t be sanding.  Here are the pieces joined and sitting in the engine bay.

It was now time to start sculpting it.  I drew out some guide lines and cut big chunks out with a knife but sanded the rest.

The top part is narrower than the bottom because there is a ½ inch piece of rubber around the panel filter and the top piece will be on top of this rubber section so that it holds the filter in place.  Here it is in the car again.

Once I was satisfied with the basic shape, I needed to start cutting it in sections.  The reason for this is because I’m going to cover it with bondo and make them into molds which I can fiberglass over.  I will then join the fiberglass pieces together after they have hardened.  When making molds, you can not have any areas that curve in because you won’t be able to pull the fiberglass piece off of the mold.  For instance, the very front part of the scoop (the pink foam) has curves going in towards the center of the scoop to help guide the air so the mold needs to be such that I can pull the fiberglass piece straight off the front of it.  Here are the pieces that I cut apart but I also realized that I need to cut the bottom piece in half as well – which will make five separate pieces.

However, after I applied bondo and started sanding the top part of the scoop, I soon realized that I needed to join those pieces back together so that all the lines matched up and to insure that the fiberglass pieces matched up correctly.  For the front part of the scoop, I re-cut the separation line with a razor blade each time I bonded over it.  I did this before the bondo hardened all the way.  The pic below shows the challenges that I was facing with the pink foam.  Almost everytime I sanded it I ended up sanding too much and getting into the foam.  The only way to fix it is too remove some of the foam in that spot, fill it in with bondo, and re-sand.

The pieces are a little bit further along than this right now but not much.  I was really hoping to get started on fiberglassing them today this weekend but you can’t fight mother nature!